1. Technical Field
The present invention relates to surface mount technology (SMT), and more particularly, to an improved pad used for mounting a surface mounted component (SMC) on a circuit board.
2. Description of Related Art
In recent years, surface mount technology (SMT) is being widely used in electronic device manufacturing. SMT is a method for assembling surface mounted components (SMC) onto the surface of printed circuit boards (PCBs). A pin or solder ball of a SMC is usually smaller than its leaded counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of balls (ball grid arrays, BGAs, for example), or terminations on the body of the component.
Ball grid arrays (BGA) accommodates the demands of SMT, and resolves the applications with high density, lower thermal resistance, low inductance leads, improved high speed performances, multiple functions, and high I/O count. However, one disadvantage of the BGA is that the solder balls of the BGA cannot flex in the way that longer leads can, and there is only one juncture between the solder balls and the pads, thus the solder joints fracture (solder-off) easily. Another disadvantage is that once the BGA components are soldered, it is very difficult to detect soldering faults, thus, a quality of the soldering cannot be ensured. Pseudo soldering, and excess solder connections occurs frequently in BGA solder process. These disadvantages which limits the application of BGA also occurs in other surface-mount packaging.
Common pads have different configurations due to varied configurations of the contacts of the electronic elements, such as a circle, a square, a teardrop, and so on. The size of the pads is usually larger than the size of the contacts of the electronic elements corresponding to the pads. When soldering the electronic elements to the circuit board, the contacts of the electronic elements may slide on the pads. As a result, accurate positioning of the electronic elements cannot be assured, pseudo soldering, solder-off, and excess solder connections will also happen.
What is needed, therefore, is an improved pad capable of accurately positioning the electronic element and not become disconnected from the contacts of the electronic element.